1. Field of the Invention
This invention relates generally to nozzles for spraying liquids and it relates more specifically to an improvement that enhances the formation of bubbles in the fluid discharged by a simplex pressure atomizer or spray nozzle.
2. Background Art
Nozzles of this type are well known in the prior art. An essential feature of simplex spray nozzles or atomizers is an interior space known as a swirl chamber. The swirl chamber usually has a generally cylindrical shape with a closed base surface at one end and a tapered or spherical surface at the other end; a discharge orifice forms an exit from the chamber at or near the apex of the tapered or spherical surface. One or more inlet passages admit liquid under pressure into the chamber in a direction generally tangential to the cylindrical axis. The tangential passages create a swirling fluid flow within the chamber, in the nature of a whirlpool; the whirlpool effect in turn creates a central low-pressure area that draws external air into the chamber through the discharge orifice. The low-pressure area that is created in this manner results in the formation of a central vortex in which an air core is surrounded by swirling liquid. It is well known that the interaction of air and liquid in the central vortex in turn produces a liquid spray made up of a myriad of tiny droplets of liquid as the contents of the swirl chamber are discharged continuously through the discharge orifice. In some prior nozzles, fluid has passed axially outwardly from such a swirl chamber into another chamber prior to passing through the discharge orifice. However, such two-chambered nozzles have had neither the structural nor the functional attributes of the present invention.
For certain applications, a spray pattern made up of tiny droplets of liquid is entirely satisfactory. For other applications such as for use in spraying oil into the combustion areas of gas turbine engines, oil burners and the like, sprays having different characteristics are preferred. It is particularly desirable to provide aerated sprays for combustion applications. This can be achieved by generating a spray containing bubbles wherein each bubble is a thin film of liquid surrounding an entrapped volume of air. It is known that sprays containing bubbles display enhanced and desirable combustion characteristics. This is believed to be due to improved air/fuel mixing and to more favorable stoichiometric ratios within the spray where ignition and burning occur. However, desirable levels of bubble formation are not readily obtainable in prior art nozzles of the simplex type, or with other known nozzle designs such as those in which air must be injected into the nozzle.